Selective Valorization of 5-Hydroxymethylfurfural to 2,5-Diformylfuran Using Atmospheric O2 and MAPbBr3 Perovskite under Visible Light

Recent progress of metal halide perovskite materials in heterogeneous photocatalytic organic reactions

Photocatalytic technology is widely regarded as an important way to utilize solar energy and achieve carbon neutrality, which has attracted considerable attentions in various fields over the past decades. Metal halide perovskites (MHPs) are recognized as "superstar" materials due to their exceptional photoelectric properties, readily accessible and tunable structure, which made them intensively studied in solar cells, light-emitting diodes, and solar energy conversion fields. Since 2018, increased attention has been focused on applying the MHPs as a heterogeneous visible light photocatalyst in catalyzing organic synthesis reactions. In this review, we present an overview of photocatalytic technology and principles of heterogeneous photocatalysis before delving into the structural characteristics, stability, and classifications of MHPs. We then focus on recent developments of MHPs in photocatalyzing various organic synthesis reactions, such as oxidation, cyclization, C-C coupling etc., based on their classifications and reported reaction types. Finally, we discuss the main limitations and prospects regarding the application of metal halide perovskites in organic synthesis.

5-Hydroxymethylfurfural and its Downstream Chemicals: A Review of Catalytic Routes

Biomass assumes an increasingly vital role in the realm of renewable energy and sustainable development due to its abundant availability, renewability, and minimal environmental impact. Within this context, 5-hydroxymethylfurfural (HMF), derived from sugar dehydration, stands out as a critical bio-derived product. It serves as a pivotal multifunctional platform compound, integral in synthesizing various vital chemicals, including furan-based polymers, fine chemicals, and biofuels. The high reactivity of HMF, attributed to its highly active aldehyde, hydroxyl, and furan ring, underscores the challenge of selectively regulating its conversion to obtain the desired products. This review highlights the research progress on efficient catalytic systems for HMF synthesis, oxidation, reduction, and etherification. Additionally, it outlines the techno-economic analysis (TEA) and prospective research directions for the production of furan-based chemicals. Despite significant progress in catalysis research, and certain process routes demonstrating substantial economics, with key indicators surpassing petroleum-based products, a gap persists between fundamental research and large-scale industrialization. This is due to the lack of comprehensive engineering research on bio-based chemicals, making the commercialization process a distant goal. These findings provide valuable insights for further development of this field.

Structural Modification Strategies, Interfacial Charge-Carrier Dynamics, and Solar Energy Conversion Applications of Organic-Inorganic Halide Perovskite Photocatalysts

Over the past few decades, organic-inorganic halide perovskites (OIHPs) as novel photocatalyst materials have attracted intensive attention for an impressive variety of photocatalytic applications due to their excellent photophysical (chemical) properties. Regarding practical application and future commercialization, the air-water stability and photocatalytic performance of OIHPs need to be further improved. Accordingly, studying modification strategies and interfacial interaction mechanisms is crucial. In this review, the current progress in the development and photocatalytic fundamentals of OIHPs is summarized. Furthermore, the structural modification strategies of OIHPs, including dimensionality control, heterojunction design, encapsulation techniques, and so on for the enhancement of charge-carrier transfer and the enlargement of long-term stability, are elucidated. Subsequently, the interfacial mechanisms and charge-carrier dynamics of OIHPs during the photocatalytic process are systematically specified and classified via diverse photophysical and electrochemical characterization methods, such as time-resolved photoluminescence measurements, ultrafast transient absorption spectroscopy, electrochemical impedance spectroscopy measurements, transient photocurrent densities, and so forth. Eventually, various photocatalytic applications of OIHPs, including hydrogen evolution, CO2 reduction, pollutant degradation, and photocatalytic conversion of organic matter.

Photocatalysis Based on Metal Halide Perovskites for Organic Chemical Transformations

Heterogeneous photocatalysts incorporating metal halide perovskites (MHPs) have garnered significant attention due to their remarkable attributes: strong visible-light absorption, tuneable band energy levels, rapid charge transfer, and defect tolerance. Additionally, the promising optical and electronic properties of MHP nanocrystals can be harnessed for photocatalytic applications through controlled crystal structure engineering, involving composition tuning via metal ion and halide ion variations, dimensional tuning, and surface chemistry modifications. Combination of perovskites with other materials can improve the photoinduced charge separation and charge transfer, building heterostructures with different band alignments, such as type-II, Z-scheme, and Schottky heterojunctions, which can fine-tune redox potentials of the perovskite for photocatalytic organic reactions. This review delves into the activation of organic molecules through charge and energy transfer mechanisms. The review further investigates the impact of crystal engineering on photocatalytic activity, spanning a diverse array of organic transformations, such as C-X bond formation (X = C, N, and O), [2 + 2] and [4 + 2] cycloadditions, substrate isomerization, and asymmetric catalysis. This study provides insights to propel the advancement of metal halide perovskite-based photocatalysts, thereby fostering innovation in organic chemical transformations.

Utilizing the Undesirable Oxidation of Lead-Free Hybrid Halide Perovskite Nanosheets for Solar-Driven Photocatalytic C(sp3)─H Activation: Unraveling the Serendipity

Hybrid halide perovskites (HHPs), whose every branch generates intrusiveness, have been utilized in solar cells from a broader perspective. However, the inclusiveness of employing HHP as a photocatalyst is in its initial stage. This study mainly focuses on the unexpected utilization of, so far, undesirable material vacancy-ordered MA2SnBr6 quantum dots synthesized from MASnBr3 nanosheets. Here, the quantum confinement grounded a large blue shift in ultraviolet (UV) and photoluminescence (PL) spectra with a Stokes shift of 420 meV, where the band gap increase is observed as size decreases in MA2SnBr6. Remarkably, MA2SnBr6 exhibits air and moisture stability, better charge transfer, and high oxidation potential compared to MASnBr3. The first-principles-based atomistic computations reveal the strain relaxation in the Sn-Br framework that structurally stabilizes the MA2SnBr6 lattice. Furthermore, the direct band gap and strongly localized valence band edge give rise to a new potential photocatalyst MA2SnBr6 for efficient solar-driven C(sp3)─H activation of cyclohexane and toluene under ambient conditions.

Stabilizing Metal Halide Perovskites for Solar Fuel Production: Challenges, Solutions, and Future Prospects

Metal halide perovskites (MHPs) are emerging photocatalyst materials that can enable sustainable solar-to-chemical energy conversion by virtue of their broad absorption spectra, effective separation/transport of photogenerated carriers, and solution processability. Although preliminary studies show the excellent photocatalytic activities of MHPs, their intrinsic structural instability due to the low formation energy and soft ionic nature is an open challenge for their practical applications. This review discusses the latest understanding of the stability issue and strategies to overcome this issue for MHP-based photocatalysis. First, the origin of the instability issue at atomic levels and the design rules for robust structures are analyzed and elucidated. This is then followed by presenting several different material design strategies for stability enhancement, including reaction medium modification, material surface protection, structural dimensionality engineering, and chemical composition engineering. Emphases are placed on understanding the effects of these strategies on photocatalytic stability as well as the possible structure-performance correlation. Finally, the possible future research directions for pursuing stable and efficient MHP photocatalysts in order to accelerate their technological maturity on a practical scale are outlined. With that, it is hoped to provide readers a valuable snapshot of this rapidly developing and exciting field.

High-efficiency visible-light-driven oxidation of primary C-H bonds in toluene over a CsPbBr3 perovskite supported by hierarchical TiO2 nanoflakes

Photocatalytic oxidation of toluene to valuable fine chemicals is of great significance, yet faces challenges in the development of advanced catalysts with both high activity and selectivity for the activation of inert C(sp3)-H bonds. Halide perovskites with remarkable optoelectronic properties have shown to be prospective photoactive materials, but the bulky structure with a small surface area and severe recombination of photogenerated electron-hole pairs are obstacles to application. Here, we fabricate a hierarchical nanoflower-shaped CsPbBr3/TiO2 heterojunction by assembling CsPbBr3 nanoparticles on 2D TiO2 nanoflake subunits. The design significantly downsizes the size of CsPbBr3 from micrometers to nanometers, and forms a type II heterojunction with intimate interfacial contact between CsPbBr3 and TiO2 nanoflakes, thereby accelerating the separation and transfer of photogenerated charges. Moreover, the formed hierarchical heterojunction increaseslight absorption by refraction and scattering, offers a large surface area and enhances the adsorption of toluene molecules. Consequently, the optimized CsPbBr3/TiO2 exhibits a high performance (10 200 μmol g-1 h-1) for photocatalytic toluene oxidation with high selectivity (85%) for benzaldehyde generation under visible light. The photoactivity is about 20 times higher than that of blank CsPbBr3, and is among the best photocatalytic performances reported for selective oxidation of toluene under visible light irradiation.

Radical-Mediated Photocatalysis for Lignocellulosic Biomass Conversion into Value-Added Chemicals and Hydrogen: Facts, Opportunities and Challenges

Photocatalytic biomass conversion into high-value chemicals and fuels is considered one of the hottest ongoing research and industrial topics toward sustainable development. In short, this process can cleave Cβ -O/Cα -Cβ bonds in lignin to aromatic platform chemicals, and further conversion of the polysaccharides to other platform chemicals and H2 . From the chemistry point of view, the optimization of the unique cooperative interplay of radical oxidation species (which are activated via molecular oxygen species, ROSs) and substrate-derived radical intermediates by appropriate control of their type and/or yield is key to the selective production of desired products. Technically, several challenges have been raised that face successful real-world applications. This review aims to discuss the recently reported mechanistic pathways toward selective biomass conversion through the optimization of ROSs behavior and materials/system design. On top of that, through a SWOT analysis, we critically discussed this technology from both chemistry and technological viewpoints to help the scientists and engineers bridge the gap between lab-scale and large-scale production.

Crystal growth, phase transition, and nuclear magnetic resonance of organic-inorganic hybrid perovskite NH2(CH3)2CdCl3

Understanding the physicochemical properties of organic-inorganic hybrid materials is essential to promote their applications. In this study, a single crystal of NH2(CH3)2CdCl3 was grown, and it exhibited a monoclinic structure. Its phase transition temperatures were 460 and 470 K, and it showed sufficient thermal stability. The changes in the NMR chemical shifts of each atom in the crystal with increasing temperature were determined; the chemical shift of 1H of NH2 in the NH2(CH3)2 cation changed with temperature, which was correlated to the changes in the chemical shift of 14N in NH2. The change in 113Cd chemical shifts indicate the change of six Cl atoms around Cd in CdCl6. Therefore, the change in the coordination geometry of CdCl6 is attributed to the change in the N-H⋯Cl hydrogen bond between the NH2(CH3)2 cation and CdCl6 anion. In addition, the 13C activation energies Ea obtained from the spin-lattice relaxation time T1ρ values are smaller than those of the 1H Ea values, suggesting that is free compared to 1H in the cation. We believe that this study furthers our fundamental understanding of organic-inorganic hybrid materials to promote their practical solar cell applications.

Tailored BiVO4 Photoanode Hydrophobic Microenvironment Enables Water Oxidative H2 O2 Accumulation

Direct photoelectrochemical 2-electron water oxidation to renewable H₂ O₂ production on an anode increases the value of solar water splitting. BiVO₄ has a theoretical thermodynamic activity trend toward highly selective water oxidation H₂ O₂ formation, but the challenges of competing 4-electron O₂ evolution and H₂ O₂ decomposition reaction need to overcome. The influence of surface microenvironment has never been considered as a possible activity loss factor in the BiVO₄ -based system. Herein, it is theoretically and experimentally demonstrated that the situ confined O₂ , where coating BiVO₄ with hydrophobic polymers, can regulate the thermodynamic activity aiming for water oxidation H₂ O₂ . Also, the hydrophobicity is responsible for the H₂ O₂ production and decomposition process kinetically. Therefore, after the addition of hydrophobic polytetrafluoroethylene on BiVO₄ surface, it achieves an average Faradaic efficiency (FE) of 81.6% in a wide applied bias region (0.6-2.1 V vs RHE) with the best FE of 85%, which is 4-time higher than BiVO₄ photoanode. The accumulated H₂ O₂ concentration can reach 150 µm at 1.23 V versus RHE under AM 1.5 illumination in 2 h. This concept of modifying the catalyst surface microenvironment via stable polymers provides a new approach to tune the multiple-electrons competitive reactions in aqueous solution.

Photocatalysis of Cr- and Fe-Doped CeO2 Nanoparticles to Selective Oxidation of 5-Hydroxymethylfurfural

Oxygen vacancies (V_o) present in CeO₂ nanoparticles (NPs) can effectively boost their photocatalytic activity under ultraviolet (UV) light. To improve photocatalytic performance, Cr- and Fe-doped CeO₂ NPs with increased V_o were prepared using a simple method of doping Cr and Fe ions into CeO₂ NPs, which was confirmed by an in-depth analysis of the structural and electronic changes. Through photocatalytic degradation (PCD) experiments with 5-hydroxymethylfurfural (HMF), we found that the PCD rates of the two doped CeO₂ NPs were faster than that of the CeO₂ NPs. In addition, the conversion of HMF to 2,5-furandicarboxylic acid (FDCA) using the doped CeO₂ NPs occurred only through the mechanism of the selective oxidation to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), exhibiting better efficiency than using CeO₂ NPs.

MIL-47(V)-derived carbon-doped vanadium oxide for selective oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran

The development and transformation of biomass-derived platform compounds is a sustainable way to deal with the fossil fuel crisis. 5-Hydroxymethylfurfural (HMF) can be reduced or oxidized to produce many high-value compounds; however, it is challenging to effectively produce 2,5-diformylfuran (DFF) due to overoxidation. In this work, a carbon-doped V₂O₅ (C-V₂O₅) material was obtained through pyrolysis of MIL-47(V) nanorods, a typical metal-organic framework material. The X-ray diffraction patterns and X-ray photoelectron spectra showed that the graphitized carbon species were incorporated in C-V₂O₅. High-efficiency HMF oxidation, high specific selectivity for DFF and excellent recycling could be achieved with the C-V₂O₅ catalyst. Fourier-transform infrared spectroscopy combined with density functional theory (DFT) calculation revealed that graphitized carbon weakens the VO bond and promotes the formation of oxygen vacancies in C-V₂O₅, thus improving the catalytic activity in the oxidation of furfuryl alcohols. The V⁴⁺ induced by oxygen vacancies will be oxidized by O₂ to form V⁵⁺, so that the cycle can be realized. It exhibits remarkable selectivity in the oxidation of different alcohols produced from biomass based on the relatively constant active sites in C-V₂O₅.

Deep eutectic solvent assisted fabrication of zirconium phytate thin nanosheets for important biomass transformations

Utilization of naturally occurring resources to construct functional catalytic materials is significantly important, and facile and environmental-benign strategies are highly desired to afford the materials having a specific structure and good catalytic activity. Herein, we reported an innovative deep eutectic solvent (DES)-assisted strategy to synthesize zirconium phytate with a thin nanosheet structure (denoted as Zr-Phy-DES) using plant-originated phytic acid (PhyA) as the renewable building block. This strategy was eco-friendly and adjustable owing to the designability of DESs. The Zr-Phy-DES as an acidic catalyst showed high activity on two important biomass transformations, i.e., dehydration of carbohydrates and Meerwein-Ponndorf-Verley reduction of ethyl levulinate. Interestingly, Zr-Phy-DES showed higher catalytic performance than the zirconium phytates prepared in ethylene glycol and N,N-dimethylformamide, confirming the advantage of DESs for preparing functional materials. Notably, the unique feature of this proposed strategy is that renewable catalysts are prepared in an environmental-benign solvent for efficiently catalyzing biomass transformation.

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An eco-friendly strategy for preparing catalytic materials with a specific structure

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The catalytic activity of the prepared materials varied with the type of solvents

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The material prepared in deep eutectic solvent showed better performance

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Catalytic materials from natural resources and green solvents to convert biomass

Electro- and Photocatalytic Oxidative Upgrading of Bio-based 5-Hydroxymethylfurfural

Conversion of biomass into biofuels and high value-added chemicals is a promising strategy to solve the increasingly deteriorating environmental problems caused by fossil energy consumption. The development of efficient technologies and methods is the premise and guarantee to realize the high-value conversion of biomass. 5-Hydroxymethylfurfural (HMF), as a versatile biomass platform compound, is generated via dehydration of hexoses (e. g., fructose and glucose) derived from cellulosic biomass. This Review gives an overview of the advances and challenges of electro- and photocatalytic oxidation of biomass-derived HMF to high-value chemicals such as 2,5-formylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA). These strategies and methods for the preparation of high-value chemicals by electro- and photocatalytic oxidation of HMF, coupled with, for example, hydrogen evolution reaction, organic substrate reduction, CO₂ reduction reaction, or N₂ reduction reaction, were summarized and discussed. Moreover, the catalytic efficiency and mechanism of different types of catalysts were also introduced in these conversion systems.

Triplet Energy Transfer from Lead Halide Perovskite for Highly Selective Photocatalytic 2 + 2 Cycloaddition

Triplet excitons are generally confined within a semiconductor. Hence, solar energy utilization via direct triplet energy transfer (TET) from semiconductors is challenging. TET from lead halide perovskite semiconductors to nearby organic molecules has been illustrated with ultrafast spectroscopy. Direct utilization of solar energy, i.e., visible light, via TET for photocatalysis is an important route but has not yet been demonstrated with lead halide perovskite semiconductors. Here, we show that a photocatalytic reaction, focusing on a 2 + 2 cycloaddition reaction, can been successfully demonstrated via TET from lead halide perovskite nanocrystals (PNCs). The triplet excitons are shown to induce a highly diastereomeric syn-selective 2 + 2 cycloaddition starting from olefins. Such photocatalytic reactions probe the TET process previously only observed spectroscopically. Moreover, our observation demonstrates that bulk-like PNCs (size, >10 nm; PL = 530 nm), in addition to quantum-confined smaller PNCs, are also effective for TET. Our findings may render a new energy conversion pathway to employ PNCs via direct TET for photocatalytic organic synthesis.

Organic building blocks at inorganic nanomaterial interfaces

This tutorial review presents our perspective on designing organic molecules for the functionalization of inorganic nanomaterial surfaces, through the model of an "anchor-functionality" paradigm. This "anchor-functionality" paradigm is a streamlined design strategy developed from a comprehensive range of materials (e.g., lead halide perovskites, II-VI semiconductors, III-V semiconductors, metal oxides, diamonds, carbon dots, silicon, etc.) and applications (e.g., light-emitting diodes, photovoltaics, lasers, photonic cavities, photocatalysis, fluorescence imaging, photo dynamic therapy, drug delivery, etc.). The structure of this organic interface modifier comprises two key components: anchor groups binding to inorganic surfaces and functional groups that optimize their performance in specific applications. To help readers better understand and utilize this approach, the roles of different anchor groups and different functional groups are discussed and explained through their interactions with inorganic materials and external environments.

CsPbBr3 perovskite quantum dots as a visible light photocatalyst for cyclisation of diamines and amino alcohols: an efficient approach to synthesize imidazolidines, fused-imidazolidines and oxazolidines

We report the synthesis of highly stable CsPbBr3QD based photocatalysts using dibromoisocyanuric acid (DBI) as a benign non-toxic bromide precursor.

Selective photocatalytic aerobic oxidation of methane into carbon monoxide over Ag/AgCl@SiO2

Design of active catalysts for chemical utilization of methane under mild conditions is of great importance, but remains a challenging task. Here, we prepared a Ag/AgCl with SiO₂ coating (Ag/AgCl@SiO₂) photocatalyst for methane oxidation to carbon monoxide. High carbon monoxide production (2.3 μmol h⁻¹) and high selectivity (73%) were achieved. SiO₂ plays a key role in the superior performance by increasing the lifetime of the photogenerated charge carriers. Based on a set of semi in situ infrared spectroscopy, electron paramagnetic resonance, and electronic property characterization studies, it is revealed that CH₄ is effectively and selectively oxidized to CO by the in situ formation of singlet ¹O₂via the key intermediate of COOH*. Further study showed that the Ag/AgCl@SiO₂ catalyst could also drive valuable conversion using real sunlight under ambient conditions. As far we know, this is the first work on the application of SiO₂ modified Ag/AgCl in the methane oxidation reaction.

The Ag/AgCl@SiO₂ catalyst exhibits excellent photocatalytic activity in selective aerobic oxidation of methane to carbon monoxide with high selectivity, and extended real light simulation feasibility shows potential in practical application.

Unsaturated NiII Centers Mediated the Coordination Activation of Benzylamine for Enhancing Photocatalytic Activity over Ultrathin Ni MOF-74 Nanosheets

Creating accessible unsaturated active sites in metal-organic frameworks (MOFs) holds great promise for developing highly efficient catalysts. Herein, ultrathin Ni MOF-74 nanosheets (NMNs) with high-density coordinatively unsaturated Ni^II centers are prepared as a photocatalyst. The results of in situ ATR-IR, Raman, UV-vis DRS, and XPS suggest that abundant Ni^II centers can act as the active sites for boosting benzylamine (BA) activation via forming -Ni-NH₂- coordination intermediates. The generation of coordination intermediates assists the transfer of photo-generated holes to BA molecules for producing BA cation free radicals, better impelling the breaking of N-H bonds and the photooxidation of BA molecules. The photo-generated electrons further activate O₂ molecules to O₂^•- radicals for triggering the reaction. The experiments reveal that the coordination activation of BA molecules may be a rate-determining step on NMNs rather than the adsorption and activation of O₂ molecules. Moreover, NMNs possess a better ability for the separation of photo-generated carriers in comparison with bulk Ni MOF-74 (NMBs). As a result, NMNs achieve a kinetic rate constant of 0.538 h^-1 for the photocatalytic oxidative coupling of BA under visible light, about 50 times higher than that of NMBs (0.0011 h^-1). Finally, a probable synergetic catalytic mechanism with coordination activation and photocatalysis is discussed on a molecular level. This study not only highlights the importance of coordination activation for heterogeneous photocatalysis but also affords an inspiration for building ultrathin MOF nanosheets.

High-efficiency synthesis of 5-hydroxymethylfurfural and 2,5-diformylfuran from fructose over magnetic separable catalysts

In this work, a sulfonic acid-functionalized magnetic separable solid acid (Fe₃O₄@SiO₂-SO₃H) was synthesized, characterized, and tested for fructose conversion to 5-hydroxymethylfurfural (HMF). Results indicated that the prepared catalyst had a good efficacy for fructose dehydration to HMF due to its larger specific surface area, appropriate acid amount and homogeneous acid distribution. The maximum HMF yield of this work was 96.1 mol%. It was obtained at 120 °C for 1.5 h with 100 mol% fructose conversion. More importantly, the produced HMF could be further in-situ oxidized into 2,5-diformylfuran (DFF) after the replacing of the Fe₃O₄@SiO₂-SO₃H with a ZnFeRuO₄ catalyst, and the highest DFF yield of 90.2 mol% (based on initial fructose) was obtained after reaction another 8.5 h. The production of DFF from fructose through the above two consecutive steps avoids the intermediate HMF separation, which saves time and energy. In addition, both Fe₃O₄@SiO₂-SO₃H and ZnFeRuO₄ catalysts exhibited satisfied stability in the recycling experiments, which can be reused at least for five times with the HMF and DFF yield loss<5.3% and 3.3%, respectively. Finally, the plausible reaction mechanisms for fructose conversion to HMF or DFF over Fe₃O₄@SiO₂-SO₃H or/and ZnFeRuO₄ catalysts were also proposed in this work.

Nanomaterial catalysts for organic photoredox catalysis-mechanistic perspective

Solar energy conversions play a vital role in the renewable energy industry. In recent years, photoredox organic transformations have been explored as an alternative way to use solar energy. Catalysts for such photocatalytic systems have evolved from homogeneous metal complexes to heterogeneous nanomaterials over the past few decades. Herein, three important carrier transfer mechanisms are presented, including charge transfer, energy transfer and hot carrier transfer. Several models established by researchers to understand the catalytic reaction mechanisms are also illustrated, which promote the reaction system design based on theoretical studies. New strategies are introduced in order to enhance catalytic efficiency for future prospects.

Application of Metal Halide Perovskites as Photocatalysts in Organic Reactions

This review summarizes the current status of the application of metal halide perovskites (MHPs) as photocatalysts in organic syntheses/transformations. It is shown that the optimal and unique electronic properties of MHPs can be advantageously used in several reaction types providing pros with respect to traditional photocatalysts. While still being at infancy, such field of application of MHPs as effective photocatalysts will for sure become a central research topic in the forthcoming years, thanks also to their rich structural and chemical tunability, which may provide tailored materials for most of the envisaged organic reactions.

Visible-Light-Mediated Oxidative Amidation of Aldehydes by Using Magnetic CdS Quantum Dots as a Photocatalyst

A magnetic CdS quantum dot (Fe₃ O₄ /polydopamine (PDA)/CdS) was synthesized through a facile and convenient method from inexpensive starting materials. Characterization of the prepared catalyst was performed by means of FTIR spectroscopy, XRD, SEM, TEM, energy-dispersive X-ray spectroscopy, and vibrating-sample magnetometer techniques. Fe₃ O₄ /PDA/CdS was found to be a highly active photocatalyst for the amidation of aromatic aldehydes by using air as a clean oxidant under mild conditions. The photocatalyst can be recovered by magnetic separation and successfully reused for five cycles without considerable loss of its catalytic activity.